In general, noodles having much water content tend to be spoiled by microorganisms such as bacteria and molds. Therefore, in order to keep a shelflife of the noodles even at room temperature for a long term over several months, the noodles have often been dried and the water content has been reduced by hot-air drying, sun drying, frying and vacuum drying. However, once the water content of the noodles has been reduced, it would be difficult to obtain the desirable texture of non-dried fresh noodles even if the dried noodles were rehydrated and restored for eating with water or hot water. Accordingly, research and development on the wet noodles which can be preserved even at room temperature without drying the fresh noodles has been continued.
The wet noodles are called, generally, fresh noodles and are directed to boiled noodles, steamed noodles, raw noodles having much water content, or noodles having slightly reduced water content in comparison with the foregoing noodles, and "desirable texture of the fresh noodles" referred in this specification is directed to the texture of noodles just cooked by boiling or steaming, and particular to the texture on "smoothness" and "stickiness" of the noodles, in addition to "stiffness" and "elasticity" thereof.
As methods to preserve the wet fresh noodles for several months at room temperature, there have been known methods, i.e., a method of adding bacteriostat(s), such as propyleneglycol, a method of sterilizing by retort, and a method of combining pH adjustment with heat sterilization. However, the former method of adding bacteriostat(s) will not provide a good image to consumers in view of using additives, and the latter method of so-called retort sterilization that conducts sterilization for over 4 minutes at 120 .degree. C. or similar conditions is not preferable, because the color of the noodles becomes dark and the desirable texture of noodles is lost. Further, in the method for improving shelflife by using both pH adjustment (to acidify the noodles) and heat sterilization, "stiffness" and "elasticity" are lost, then the desirable texture of the noodles is also not obtained, because the water penetration into the inside of the noodle strands after the sterilizing step and the moisture gradient between the inside and the outside of the noodle strands is eliminated.
Then, the present inventors developed a process for producing wet noodles having a longer shelflife even at a room temperature, and having "stiffness" and "elasticity" by a method comprising the steps of preparing noodles by adding alkaline agents and alginic acids to the flours, acid-treating the noodles so obtained, and heat-sterilizing them (See, Japanese Patent Application No. 3-174129). However, according to this invention, "smoothness" and "stickiness" of the noodles were insufficient, though "stiffness" and "elasticity" of the noodles can be obtained well.
Although techniques to incorporate alginic acids into the noodles are disclosed in the prior art of Japanese Patent Publication No. 61-12662, Japanese Patent Publication No. 1-49472, Japanese Patent Provisional Publication No. 62-79749, and Switzerland Patent Application No. 02444/90-9, said techniques are directed to the action of calcium salts against the noodles to which alginic acids are added. These methods were making use of insolubilization and gelation of alginic acids due to the formation of calcium alginates which are calcium salts of alginic acids. However, "stiff" and "elastic" texture of the noodles and a longer shelflife at room temperature, which can be obtained by adding alginic acids to noodles and treating them with acids along with disclosure of the patent application (Japanese Patent Application No. 3-174129) by the present inventors, could not be obtained by the methods aforementioned.